A study of Southern California middle school students found that those who see ads, billboards, or signs for medical marijuana were more likely to think about or smoke pot than those who see no advertising, researchers said Monday.

Surveys from more than 8,214 students who attended 16 Southern California middle schools during 2010 and 2011 were analyzed by researchers with the RAND corporation. The youths were asked in 2010, then again in 2011 about their exposure to medical marijuana advertising, use and their intentions about whether to use it in the future.

During the first survey, 22 percent of the students reported seeing at least one advertisement for medical marijuana over the past three months. The following year, the rate jumped to 30 percent.

Based on the answers, researchers said that seeing advertisements for medical marijuana was related to adolescents’ intentions to use or actually use marijuana one year later.

Society’s increasing lenient attitudes on marijuana use could lead youth into believing there are no adverse effects, said Elizabeth D’Amico, lead author of the study and senior behavioral scientist at RAND, a non profit research organization.

“I’m sure there are factors that contribute to marijuana use that we don’t know,” D’Amico said. “We need to start educating our youth better about medical marijuana and what it means. We need to think about policies around advertising, which we have for tobacco and alcohol.”

D’Amico said researchers could not determine if those teens who were predisposed to use marijuana paid more attention to advertising or whether the advertising may have influenced their decisions.

Another recent study published in the British medical journal Lancet, found that passage of state medical marijuana laws does not increase adolescent use of marijuana. Pot use in states where there were no medical marijuana laws did not differ from states where medical marijuana laws were passed, according to Lancet researchers.

As medical marijuana continues to be examined, there will likely be increased discussions and regulations about advertising, said Christopher Brown, a spokesman with Americans for Safe Access,an organization that works to see the safe and legal access to cannabis (marijuana) for therapeutic uses and research.

“We don’t want people to think of medical marijuana more than it should be thought of,” Brown said.

As laws surrounding medical marijuana change and expand, Brown said the industry expects more regulations to follow.

“We’re definitely at a point where the decision being made in the next couple of years, will likely set the rules for the next couple of decades,” Brown said. “We want to regulate medical marijuana in smart ways that don’t cause restrictions for patients. “

D’Amico and a team of researchers plan to follow the same group of youth for years. Many are now in the 11th grade. A follow up study based on their surveys from 2012 and 2013 will be released soon.

But the 2010-2011 study already shows that policies and discussions on prevention as well as limited advertising about marijuana need to start taking place, D’Amico said.

“I’m not saying alcohol and marijuana are bad, but I think educating youth so they can make healthy choices for themselves should start now,” she said. “Youth know you should never drink and drive, but they don’t believe marijuana has the same kind of consequences as alcohol does.”